FIG. 1 shows a prior art handrail driving unit and handrail guiding device of an escalator system. Pulley 2 for driving handrail 1 is rotated by a main sprocket of a motor via driving chain 6. The inner surface of handrail 1 is urged against the outer peripheral surface of driving pulley 2 by pressing rollers 5. As driving pulley 2 rotates, handrail 1 moves by a frictional force between the peripheral surface of driving pulley 2 and the inner surface of handrail 1.
In a passenger conveying area, handrail 1 is supported by continuous guiding means. However, in a return area (shown in FIG. 1), handrail 1 is supported discontinuously by guiding means in order to reduce moving resistance. Especially, upper handrail guiding device 4 and lower handrail guiding device 3 are provided near driving pulley 2 for guiding the movement of handrail 1 while reducing the moving resistance.
FIGS. 2a and 2b are side views showing respectively upper handrail guiding device 4 and lower handrail guiding device 3. Upper and lower handrail guiding devices 4 and 3 commonly include curved frames 8 and 12, first supporting rollers 9 coupled to curved frames 8 and 12, and second supporting rollers 10 disposed above first supporting rollers 9. Curved frames 8 and 12 are fixed to a truss by brackets 11a, 11b, 13a and 13b. Handrail 1 is placed between first supporting rollers 9 and second supporting rollers 10 in such a manner that the outer surface of handrail 1 is contactingly supported by first supporting rollers 9. Second supporting rollers 10 are spaced from the inner surface of handrail 1 at a predetermined interval and prevent handrail 1 from meandering.
When the escalator moves upward in the passenger conveying area, handrail 1 in the return area moves downward. Because driving pulley 2 provides a tensile strength to handrail 1, handrail 1 moves while being supported by first supporting rollers 9 of upper handrail guiding device 4. However, a portion of handrail 1 passing by driving pulley 2 tends to be loosened and wrinkled at lower handrail guiding device 3. So, the inner surface of handrail 1 contacts second supporting rollers 10 of lower handrail guiding device 3, thereby increasing the moving resistance of handrail 1. To solve this problem, the escalator system typically includes a device (not shown) for compensating the length of the loosened or wrinkled handrail at the lower landing zone.
When the escalator moves downward in the passenger conveying area, handrail 1 in the return area moves upward. So, a portion of handrail 1 passing by driving pulley 2 tends to be loosened and wrinkled at upper handrail guiding device 4. However, since the existing handrail length-compensating device mounted to the lower landing zone cannot cope with the wrinkling of handrail 1 at upper handrail guiding device 4, the inner surface of handrail 1 severely collides with second supporting roller 10. Thus, the inner surface of handrail 1 may be seriously damaged due to the collisions, and friction between the inner surface of handrail 1 and second supporting roller 10 sharply increases, causing deterioration of the operational stability of the escalator system.
FIG. 3 shows another prior art handrail guiding device in order to address and resolve the aforesaid problems. The prior art device comprises curved frame 14 and a plurality of supporting rollers 16 and 17 mounted to curved frame 14. Frame 14 is elastically mounted to the truss by means of spring 15. Thus, when handrail 1 moves upward in the return area, the prior art device compensates the length of loosened or wrinkled handrail 1 passing by the driving pulley by moving up and down due to spring 15. However, since supporting rollers 16 and 17 are fixedly arranged in accordance with the predetermined curvature of curved frame 14 and unitarily move up and down together with frame 14, the prior art device cannot optimally compensate the length of wrinkled handrail 1. Further, handrail 1 may be bent steeply near supporting rollers 16 and 17 positioned at the leftmost and rightmost ends (as shown in FIG. 3), causing serious physical damage to handrail 1.